The present invention relates to a tank leak detector that utilizes a precision pressure transmitter positioned in a tank. The detector precisely indicates leaks into the tank and leaks out of the tank, including evaporation loss. The detector is preferably designed for operation in underground tanks, especially previously installed tanks, where temperature stability of measurements is very good. The detector can also be operated outside the tank or as part of an automatic system that keeps the fluid in the tank at a particular level.
Various tank level detectors or leak detectors have been utilized in the past, some of which use pressure sensors immersed in the liquid to detect changes in pressure heads of columns of liquid in a tank relative to a reference during a monitoring or test time, such as taught in U.S. Pat. No. 4,739,648 to Horner. The drawback to this type of detector is that the detector must be immersed in the liquid, preventing monitoring of low levels of fluid. Other devices use a bubbling technique, such as taught in U.S. Pat. No. 4,649,739 to Horner, in which a continuous stream of bubbles of air is forced into the liquid near the bottom of the tank and the resistance to air introduction used as an indication of level of the liquid in the tank.
There is a need to provide a detector capable of operation both above and below the liquid surface. Further, there is a need to provide a detector that can reside entirely within a previously installed tank without having to dig up the tank or drain the fluid to put holes in a tank wall.